1. Field of Invention
The present invention relates to a two-parallel-channel reflector (TPCR) with focal length and disparity control, capable of capturing a dual-view image (a left side view and a right side view) of a scene after being combined with an imaging device, so as to generate a stereoscopic image, with the ability of focal length and disparity control. More particularly, a TPCR with focal length and disparity control has two parallel channels that allow an imaging device to capture a left side view and a right side view of a scene synchronously; each parallel channel is bounded by a curved outward reflecting mirror and a curved inward reflecting mirror that enables light rays into the channel to be parallelly reflected inside the channel. With the parallel channels, operators may adjust the interocular distance between the outward reflecting mirrors and the convergence angle between the view directions of the outward reflecting mirrors, so as to control the disparity and focal length during the imaging operation, without changing the dimension of the reflector.
2. Related Art
Conventional computer stereo vision uses two or more cameras to shoot images of the same scene from different view angles. The imaging devices are separated by a distance, like human eyes. The computer then calculates the depth of an object in the scene by comparing images shot by the two different cameras. This is done by shifting one image on top of the other one to find the parts that match. The shifted amount is called the disparity. The disparity at which objects in the images best match is used by the computer to calculate their depths.
A multi-view imaging system uses only one camera to calculate the depth of an object. In most cases, such a system includes specially designed mirrors to create virtual cameras. With the views captured by the physical camera and the virtual cameras, the computer can use the same scheme as in conventional computer stereo vision to calculate the depth of an object.
FIG. 1 is a schematic constitutional view of a two-channel multi-view imaging system patented by Andre Redert and Emile Hendriks in 2003. Referring to FIG. 1, a hand held camera 11 is mounted on a reflector 12 patented by Pieter O. Zanen which has a left imaging channel 121 and a right imaging channel 122 and each channel is bounded by two flat reflecting mirrors. As shown in FIG. 1, the left imaging channel 121 is bounded by a left side inward mirror 1211 and a left side outward mirror 1212, and the right imaging channel 122 is bounded by a right side inward mirror 1221 and a right side outward mirror 1222. Light rays L1 into the left imaging channel 121 reach the left side outward mirror 1212, are reflected to the left side inward mirror 1211, and are then reflected to the camera 11. Light rays L2 into the right imaging channel 122 reach the right side outward mirror 1222, are reflected to the right side inward mirror 1221, and are then reflected to the camera 11. Hence, an image generated by Redert/Hendricks' imaging system 1 contains two views of the scene, a left view and a right view.
A disadvantage of Zanen's two-channel reflector is that operators cannot adjust the disparity of the reflector. For the solution of this situation, operators need to adjust the distance between the two outward mirrors, and this requires the capability of changing the dimension of the outward mirrors dynamically, because the dimension of an outward mirror is proportional to the distance between the outward mirror and the corresponding inward mirror. For an example in FIG. 2, as the left outward mirror 1212 moves to the left farther, the thickness d1 becomes larger, and this affects the entire dimension of the two-channel reflector directly. Another disadvantage of Zanen's reflector is unable to control the convergence angle of the reflector.
FIG. 3 is a schematic view of a two-channel reflector patented by Shuzo Seo in 2005; this is an improvement of Andre Redert and Emile Hendriks' approach. Referring to FIG. 3, a mechanism is added to the two-channel reflector so that the outward mirrors can be rotated synchronously about the pivot points respectively. This rotation process is automatically performed when the lens of the camera is zoomed. As a result, the focal length of the two-channel reflector can be automatically adjusted when the lens of the camera is zoomed. This is an important invention on single-lens, multi-view imaging process. But due to the fact that flat mirrors are used for both outward reflecting and inward reflecting, Seo's invention cannot adjust disparity of the reflector either.